Within the field of cutting or chip removing machining of, above all, workpieces of metal, miscellaneous working operations occur that are based on a workpiece and a tool being set in motion in relation to each other. Although the relative motions at times may be linear or rectilinear, many operations are carried out by a combination of linear and rotary motions. Previously, two main types of motion combinations could be distinguished, viz. on one hand, rotation of a workpiece and machining of the same using a non-rotary, linearly movable tool (i.e., turning), and on the other hand rotation of a tool for the machining of a fixed workpiece (i.e., drilling and milling). Recently, numerically controlled machines have been developed, in the form of so-called MultiTask machines or TurnMill centers, which dramatically increased the possibilities of combining different relative motions when the tool is to machine the workpiece. Thus, now it is, for instance, possible to clamp the workpiece in a holder, which may alternately either be fixed in a given location, or be brought to rotate, possibly during simultaneous linear motion of the holder, at the same time as a holder for the tool may not only be rotated and/or linearly fed, but also be moved planetary (transverse fed). The planetary motion can take place irrespective of whether the tool rotates in relation to the movable holder or is locked in relation to the same (i.e., without rotating around its own axis).
The combination possibilities offered in modern machines have resulted in a fairly intense development of so-called multi-operation tools, which in one and the same set-up can machine a workpiece in a plurality of different ways, e.g., by turning, milling, drilling, etc. In such a way, the number of tool exchanges, when individual tools are returned to a magazine and a new tool is picked out from the same to replace the preceding one, can be brought down to a minimum while increasing the efficient working hours of the machine. Examples of such multi-operation tools are disclosed in, for example, German patent document no. DE 3733298 A1, U.S. Patent Application Publication No. 2004/0177491 A1, and Swedish patent document SE 523755.
A commonly occurring task within the metal-working industry is to provide a hole having at least one female thread. Such holes may be deep or shallow, and either be open in both ends or open in one end and closed in the other (so-called blind holes). Furthermore, the thread may be formed either along the entire length of the hole wall or only along a part of the same. In the latter case, the thread is usually located closest to the entering mouth of the hole.
Also for the specific task of recessing a hole and providing the same with a thread, multi-operation tools of the drill type have been proposed. Thus, U.S. Pat. No. 4,943,191 discloses a drilling tool that includes two front cutting edges formed adjacent to chip flutes for the purpose of making holes, as well as two sets of thread-cutting teeth formed adjacent to the side limiting edges of the chip flutes. However, a disadvantage of this tool is that the tool has to be discarded, or possibly be reground, as soon as either the front, hole-making cutting edges or the thread-cutting teeth behind have been worn out or otherwise become unusable, because the cutting edges as well as the teeth are integrated in a common, solid drill body. Another disadvantage is that the tool only can generate threads having a predetermined profile shape and a predetermined pitch. Thus, in order to be able to provide threads having a varying profile shape and a varying pitch, a great number of different tools have to be provided. In addition, the thread is compulsorily formed along the entire length of the recessed hole.
Furthermore, by U.S. Pat. No. 5,733,078 a drilling tool is known, which in contrast to what has been described above, makes use of replaceable cutting inserts in a long-term operable basic body. However, also in this case, the hole-making cutting edges of the tool and the thread-cutting teeth thereof are active simultaneously, because they are included in one and the same cutting insert. A consequence of this is that the front tooth of each set of teeth partially participates directly in the hole-making task, without being able to work in an already generated hole wall. This mode of operation runs the risk of giving poor dimensional accuracy in the generated thread. Another disadvantage is that the thread always becomes as long as the proper hole. In other words, the hole can never, even partially, be formed with a smooth inside.
A chip-removing tool, which includes a plurality of cutting inserts and insert seats placed one after the other in a common, flute-like chip space, is a long-edge milling cutter. However, in this case, the cutting inserts and the appurtenant insert seats are of the same type so far that all cutting inserts of the row of cutting inserts are milling inserts, which cannot machine a workpiece in another way than by milling.
The present invention aims at obviating the above-mentioned disadvantages of previously known multi-operation tools and at providing an improved tool particularly suitable for purposes of making holes and forming threads. Therefore, an object of the invention is to provide a multi-operation tool by which a hole can be recessed and immediately thereafter be provided with one or more threads.
Another object of the invention is to provide a tool that, in direct connection with the hole making, allows the formation of one or more single grooves having an arbitrary cross-section shape in the hole wall, e.g., for clamp rings, O-rings or the like. Furthermore, the tool should be able to allow the formation of holes that includes one or more threads of varying length, as well as one or several smooth, threadless sections.
Yet another object of the invention is to provide a tool by which holes can be recessed having most varying diameters, and simultaneously allow forming of one or more threads of varying profile as well as varying pitch. In a particular respect, the invention aims at increasing the flexibility of the tool so far that the same should be convertible in a simple way for other tasks than thread forming, e.g., pure drilling or hole making. Although the main object of the invention is to provide a tool for hole making and the formation of internal threads, the tool should, however, also be possible to be used for external machining, e.g., turning of male threads.
Still another object of the invention is to enable a simple and cost-effective manufacture of the tool, among other things by allowing the use of standardized components, e.g., in the form of existing drill or milling cutter-body workpieces, as well as commercially available cutting inserts that do not require modifications.